The present invention is directed towards optical scanning apparatus, such as flat-bed scanners, photocopiers and other apparatus, which employ a moveable carriage for performing an optical scanning process. In such scanning apparatus an object to be scanned (i.e., a “scannable object”) is typically placed on the upper surface of a flat, transparent platen, and the moveable carriage is moved beneath the platen to thereby optically scan the object. The optical scanning carriage assembly (or “carriage”) typically includes the lamp set which is used to illuminate the scannable object, a lens set which is used to focus light reflected from the scannable object, and a sensor array (typically a Charge-Coupled Device, or “CCD”) which is used to sense the reflected light. The sensor array generates signals in proportion to the intensity of light reflected by the scannable object, and the signals are used to generate an electronic or latent image of the scannable object.
A number of the components in the scanning carriage assembly are relatively fragile, and can be damaged by mechanical shock and/or vibration. This can occur, for example, during shipping of the optical scanning apparatus, or when the scanning apparatus is moved from one location to another. In order to reduce the chance that the carriage assembly might be damaged, many scanning apparatus are provided with a carriage locking device. Turning to FIG. 1, a prior art carriage locking device is depicted in a side sectional view. The carriage lock depicted in FIG. 1 uses a screw hole “B” which is formed in a side of the scanner carriage “A”. A bracket “D” is attached to the chassis “C” of the scanning apparatus. Bracket “D” holds knob “G”, which is configured to mate and engage with the screw hole “B” through an external thread “F” on the stem of the knob “G”. The stem of the knob “G” passes through the opening “E” formed in the chassis “C” and the bracket “D”. A compression spring “H” biases the stem of the knob “G” away from the hole “B” in the carriage “A” when the scanning apparatus is in use (as depicted in FIG. 1). When the scanning apparatus is to be transported, a user pushes the knob “G” leftwards until the end of the stem engages the hole “B”. The user then turns the knob “G” until the threaded portion “F” is seated in the hole “B”. In one variation the knob “G” is removable from the chassis “C”, while in another variation the knob “G” is held to the chassis by a retaining ring “I”.
There are a number of disadvantages to the prior art carriage locking devices. Firstly, they require the user to manually engage and disengage the lock. Accordingly, a user may be disinclined to engage the lock when the scanning apparatus is to be moved only a short distance. However, the carriage assembly can still be subjected to mechanical shock during even a short move. Further, when the knob “G” is removable from the chassis “G”, then the user may misplace or lose the knob, such that it is not available when needed. On the other hand, if the knob “G” is held to the chassis “C” by a retaining ring, then the protruding knob (as in FIG. 1) presents a potential impact point, and may actually subject the scanning apparatus to an increased risk of experiencing mechanical shock. Further, if the user forgets to release the lock before operation, there is a potential for damage to the scanning mechanism. Even if permenant damage does not occur, the device will not scan properly, which can result in increased support costs.
What is needed then is a scanner carriage locking device which achieves the benefits to be derived from similar prior art devices, but which avoids the shortcomings and detriments individually associated therewith.